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Old   October 13, 2004, 07:27
Default Meshing a previously united volume
  #1
Nicklas
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Hey!

I'm trying to mesh a volume using a "Hex Core" scheme with Tet/Hybrid elements. Because of GAMBIT's failure to mesh one specific face, no volume mesh can apparently be created.

The error message tells me that this face cannot be meshed using triangular elements.

I'm hoping that there may be some way of bypassing this problem, perhaps by choosing another scheme for meshing the face in question.

Any ideas...?
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Old   October 13, 2004, 08:22
Default Re: Meshing a previously united volume
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Jason
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I've run into this problem a couple times. Check out the face, is there any obvious reason it can't be meshed? If there's a problem area, sometimes splitting the edge near the problem area will help, or splitting the face so that the problem area gets split between two faces.

One other thing you can try is meshing the face with a quad mesh, and especially using a mapped mesh if you can. Once the face is meshed, you can split it to tri mesh. You'll probably have to delete all of the face meshes and edge meshes adjacent to this face to get this to work, and it might not work at all if the face is too complicated.

Hope this helps, Jason
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Old   October 13, 2004, 09:49
Default Re: Meshing a previously united volume
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Nicklas
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Thanks Jason!

The quad approach seems to be taking me forwards. I had to use pave schemes instead of map ones, but the mesh splitting works beautifully.

take care
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Old   October 29, 2004, 05:34
Default Re: Meshing a previously united volume
  #4
spp
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dear jason,

1. In my case by using pave scheme I was able to mesh two united volumes, but the meshed file does not open in fluent6.1. the message generated is "fatal internal error in lie 3683 in mem.c"

2. Also when I define outflow through a radiator, fluentgives message that radiator can not be imported as it has only one adjacent cell thread.
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Old   October 29, 2004, 08:26
Default Re: Meshing a previously united volume
  #5
Jason
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Have you been able to open other meshes of the same size in Fluent on that system? The message sounds more like a Fluent problem (like system setup or memory limit?) than a mesh problem, but I couldn't tell you for sure.

If you've been able to open files before, then go back to your mesh in gambit and run the volume mesh check. It'll tell you if you have any highly skewed elements or inverted elements. I've had problems where I didn't notice any error in Gambit when I meshed the volume, and then Fluent wouldn't import it because of an inverted cell.

As for the problem with the boundary condition, I'm not sure. For some reason this problem sounds familiar, but I can't think of what the cause is, or even where I've seen it before. I'm sure you've done so already, but go back to your mesh and make sure that it's faces that you're defining the boundary condition on and not edges. Make sure you've got the correct face too. Other then that, I'm not sure, but if I think of where I've heard this before I'll post it.

Good luck, Jason
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Old   November 1, 2004, 04:05
Default Re: Meshing a previously united volume
  #6
spp
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Hi Jason,

Thanks a lot for response. When I tried to solve the problem by spliting the volume and meshing separately, the message in fluent is --"unrefrenced grid, radiator and porous jump are converted to wall.As aresult transportation of radiator and porous jumps had not been successful.

I also tried boundary conditions on a group instead of faces but with no success.

--spp
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Old   November 1, 2004, 09:20
Default Re: Meshing a previously united volume
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Jason
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When you split the volume, did you make sure the "Connected" option was selected? With this option, both volumes share the same face. If they don't share the same face, then Gambit doesn't realize that there is a mesh on both sides of one face, so it doesn't see where the flow would pass through, and internal b.c.s (like radiator and porous jump) are automatically converted to walls.

You can go back and connect the faces (it's the icon where it looks like you're plugging two extension cords together) and then you'll have to fix your mesh.

I can't think of anything else, but if I think of anything I'll post it.

Hope this helps.

Jason
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Old   November 9, 2004, 01:06
Default Re: Meshing a previously united volume
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spp
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Hi Jason,

You were absolutely right. It worked. Thanks a lot.
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